Something Is Killing My Fish! Possible Mantis!

[lewiss]

Here's the story, I've lost a number of fish over the space of the 6 months I've had my tank, some down water glitches but most unexplained.. Recently my damsel was found head first in a rock crevice, quite wedged in and hard to removed, thee was little damage to it's face, but I thought I might have done that trying to remove him, but it wasn't anything to gory just a few scratches. Then I had two deaths of my shrimps, they were cleaners and I had them since I started, they were the first thing I put in! One had died what appeared to be a very violent death, and had been ripped apart. And colin the emerald crab suffered death and it turns out he was a she and was pregnant cos eggs were coming out!! . The second shrimp was just dead. My water parameters have been near perfect so far and I was happy I was finally getting there! Now this morning my dwarf angel Alice was found head first in the same crevice in a rock, nd I had some effort getting her out, I was very sad because she was a beautiful!!

So what is killing them? Am I wrong to be assuming something (ie a creature) is killing them!! My fear is it's a Mantis shrimp because about 4weeks ago I heard loud cracking like my tank glass was breaking, this only went on for about 2 weeks and I haven't heard it since, I thought it was one of the pumps. It was a loud click but only one every 3seconds, always one in a row never two.
I didn't know about mantis then!

Anyway, this is all I could come up with but having said that I've never seen anything unusual in my tank, and from the Internet it looks like u see the mantis around? Also all of these have happened after dark, middle of the night type stuff.

Help please!!

 

[xxBarneyxx]

Not ruling out a mantis completely but despite popular opinion they are not that common.

The one thing that does suggest a mantis to me is the fact that you found two fish in the same hole in the rock. This would "seem" to suggest that something dragged them in there. However it could be that you have a crab in there which either killed the fish or more likely found the fish already dead and dragged them into its hole. However with both a mantis or a crab you would expect more damage to the body.

Do you have hermit crabs or snails? Often both of these can tap their shells against the glass which results in quite a loud clicking noise.

The reason I don't think it is a mantis is that most mantis shrimps are not active at night. It also seems that most fish/invert deaths occur at night too so I think its more likely that the deaths where from natural causes and the cases where you found the bodies mangled were where they had been picked over by scavengers after dying. I would think that if a mantis had a go at both shrimp it wouldn't have left one intact.

I'm not 100% ruling out a mantis but I would highly recommend getting a second opinion on your water stats (ammonia, nitrite, also check PH, salinity and temp). Also observe the fish a couple of hours after lights out and look for signs of heavy breathing as it could be a CO2 buildup overnight and not enough oxygen in the water (fixed by adding a powerhead pointing towards the water surface to get some surface movement going).

I'm really sorry about your loses though, hopefully between yourself and the people on this forum we can get to the bottom of it and stop it from happening again.

 

[Pearsondesign]

heya, sorry ot hear about the losses

it could be a matis or a pistol shrimp. is it a quick "tap tap tp" or a single loud "tap"?

you can get special traps for catching them, or can make one yourself.
use a small sized coke bottle, bury it half in substrate so only half the neck top is out of the sand and put a piece of food, like a prawn or bit of lance fish in.
leave it over night and with any luck youll wake up to the little #28### in it. plus, youll probably end up with all sorts of other critters in ther elol

this isnt a guaranteed way of catching but it has worked in the past for many people.

not much consolation, but if you do find its a mantis shrimp please let me know as im looking for some more

good luck

 

[xxBarneyxx]

That's some good advice above about the bottle trap. Well worth giving it a go just to make sure. Don't leave too much food in it though as it will quickly foul the water, especially in a smaller tank.

 

[Pearsondesign]

That's some good advice above about the bottle trap. Well worth giving it a go just to make sure. Don't leave too much food in it though as it will quickly foul the water, especially in a smaller tank.

lol, cheers Barney, i forgot that bit
yeah i wouldnt leave it in more than one night then remove and replace the food with fresh if it didnt work.

 

[lewiss]

You actually want a mantis!!! Why?!?

I've taken the piece of rock out in the hopes it'll die within. Was that a bad idea!!

 

[xxBarneyxx]

I know a lot of people that keep mantis shrimp. If I can ever find the time and space to set up a tank I would love to keep one. They are really interesting critters and surprisingly intelligent as well.

If you have taken the rock out be careful when putting it back in the tank. The rock itself will "die" meaning that when you put it back in the tank it will cause an ammonia spike as it will no longer be cured. Depending on how big the rock is and how big the tank is this may or may not cause a problem (if its a small rock in a big tank the ammonia spike caused wouldn't be noticeable).

 

[Pearsondesign]

ive already got one bright green mantis, its only about 1 and ahalf inches at moment, but i want it to get full size

ive always been fascinated with them, cant really explain it lol

also, on a side note, they have the best eyesight of any living creature on this planet

heres an interesting article on them,
http/www.suite101.com/content/prawns-worth-more-than-just-a-sandwich-a177764

 

[seffieuk]

Zipzap, my daughter keeps a peacock mantis, very pretty and intesting to watch for a while. If your victims have been all found in the same place it is likely to be a hunter of some sort. The mantis finds it self a little hole and then tops it off with a stone, during the day it is usually guarding the hole but can be seen at night hunting, but it is always very close to its hole


Seffie x

 

[Kirsty5]

Try Googling Eunice worm - Just a thought!

One way of telling if its one is 5 antennae on the head. Try a red light at night to watch your tank as they are less sensitive to this type of light, although if you try a lazer pen, mine used to follow the pinpoint of light!

I had a marine tank for years and had some unexplained deaths, some partially eaten

(These worms are killers although never asked to be put in your tank, so please spare them a thought, although they will kill and will grow large. Mine grew from a few centimetres to a few foot and then I had to get rid. Enough was enough and it was war! I found a couple of smaller, adolescents and before they got too large, I despatched them. Not nice, but nicer for my tank occupants).